
\documentclass{dingjia}

\ctexset{autoindent=false}
\setlength\parindent{0pt}

\begin{document}
\begin{alignat*}
   t1 & \leftarrow \Pi_{city}(\sigma_{company\_name = "Small\ Bank\ Corporation"}(company))\\
  result & = \Pi_{DISTINCT\ company\_name}(company) \\
  & -{DISTINCT\ company\_name}(company \triangleright t1)
\end{alignat*}
\end{document}